Index: trac/config.py
===================================================================
--- trac/config.py	(revision 2325)
+++ trac/config.py	(working copy)
@@ -17,7 +17,7 @@
 from __future__ import generators
 
 from ConfigParser import ConfigParser
-import os.path
+import os.path, sys
 
 
 class Configuration:
@@ -28,11 +28,13 @@
     when the file has changed.
     """
 
-    def __init__(self, filename):
+    def __init__(self, filename, site_filename = = os.path.join(sys.prefix, 'share', 'trac', 'conf', 'trac.ini')):
         self.filename = filename
+        self.site_filename = site_filename
         self.parser = ConfigParser()
         self.__defaults = {}
         self.__lastmtime = 0
+        self.__lastsitemtime = 0
         self.parse_if_needed()
 
     def get(self, section, name, default=None):
@@ -81,12 +83,19 @@
         self.parser.write(open(self.filename, 'w'))
 
     def parse_if_needed(self):
-        if not self.filename:
-            return
-        modtime = os.path.getmtime(self.filename)
-        if modtime > self.__lastmtime:
-            self.parser.readfp(open(self.filename))
-            self.__lastmtime = modtime
+        files = []
+        if self.site_filename:
+            modtime = os.path.getmtime(self.site_filename)
+            if modtime > self.__lastsitemtime:
+                files.append(self.site_filename)
+                self.__lastsitemtime = modtime
+        if self.filename:
+            modtime = os.path.getmtime(self.filename)
+            if modtime > self.__lastmtime:
+                files.append(self.filename)
+                self.__lastmtime = modtime
+        if files:
+            self.parser.read(files)
 
 
 def default_dir(name):
Index: trac/test.py
===================================================================
--- trac/test.py	(revision 2325)
+++ trac/test.py	(working copy)
@@ -125,7 +125,7 @@
         self.db = InMemoryDatabase()
 
         from trac.config import Configuration
-        self.config = Configuration(None)
+        self.config = Configuration(None, None)
 
         from trac.log import logger_factory
         self.log = logger_factory('test')